Means for assembling a multiple electron gun structure for cathode ray tube



May 5, 1970 G. A. BURDICK 3,509,609 MEANS FOR ASSEMBLING' A MULTIPLE ELECTRON GUN STRUCTUBE FOR CATHODE RAY TUBE Original Filed May 51. 1966 3 Sheets-Sheet l INVENTOR. GLEN A BURDICK ATTORNEY G. A. BURDICK 3,509,609 MEANS FOR ASSEMBLING A MULTIPLE ELECTRON GUN May 5, 1970 STRUCTURE FOR CATHODE RAY TUBE Original Filed May 31, 1966 3 Sheets-Sheet 2 INVENTOR. GLEN A. BURDICK ga -W llll ATTOR N EY cs. A. BURDICK 3,509,609 MEANS FOR ASSEMBLING A MULTIPLE ELECTRON GUN May 5, 1970 STRUCTURE FOR CATHODE RAY TUBE Original Filed May 31, 1966 5 Sheets-Sheet 5 F1 5 F1-1UF J-H INVENTOR. GZEN A. BURDICK ATTORNEY ijl 57. Z I28 ELECTRODE United States Patent U.S. Cl. 29--25.19 5 Claims ABSTRACT OF THE DISCLOSURE Means for assembling a multiple electron gun structure comprising a plurality of related unipotential low-voltage focusing lens guns employing overlapping focusing electrodes. A common longitudinal central support means is utilized to provide alignment for assembling the plurality of successive cylindrical electrodes of each gun. The successive electrodes have related external diameters compatible with the common support means to facilitate alignment in sequential order from an end electrode. A plurality of external electrode support means provide cradle like aligned support for the electrodes of each gun, While related securing means position the external support means relative to the common support means to confine the electrodes in spaced alignment.

Cross-references to related applications This application is a divisional application of S.N. 553,752, filed May 31, 1966, which is assigned to the assignee of the present invention. This divisional application contains matter disclosed but not claimed in another application, S.N. 711,073, filed concurrently herewith, which application is also a division of S.N. 553,752.

Background of the invention This invention relates to electron discharge devices and more particularly to color cathode ray tube multiple electron gun structures employing unipotential low-voltage focusing lenses.

Many of the cathode ray tubes presently employed in color television display applications are of the type having an envelope with a patterned multi-phosphor cathodoluminescent screen disposed on the viewing panel thereof with an apertured structure or foraminous mask positionally spaced therefrom. Electrons from a multiple elec- Q tron gun mount structure, positioned within the envelope, are beamed through the apertured structure to discretely impinge and luminescently excite the electron-responsive phosphors of the screen. Focusing of the electron beams from the individual guns is usually achieved *by means of two cylindrical bipotential focus lenses of the familiar equidiameter type.

The focus voltage of each bipotential gun is commonly in the order of 15 to 20 percent of the anode voltage, thus with an anode voltage in excess of 20,000 volts, the focus voltage may be well above 3,000 volts. It is well known in the art that the proper focusing action of bipotential lenses is critically dependent on the ratio of the focus voltage to the respective anode voltage. To achieve the desired ratio, it is necessary in color television equipment employing color cathode ray tubes employing bipotential focusing to either regulate the anode voltage to keep it constant or to supply bleeder means for maintaining a substantially constant ratio as the beam current changes. Either one of the aforementioned procedures has the related manufacturing disadvantage of requiring special circuitry provisions in the allied equipment to accomplish the desired control. From the standpoint of display quality, electron guns employing bipotential focusing tend to bloom or produce large spot size under high beam current condition and are susceptible to degraded focus at the periphery of the screen.

In monochrome cathode ray tubes certain of the aforementioned disadvantages have been overcome by utilizing electron guns having unipotential focusing lenses. An example of this type of gun is the overlapping unipotential, focusing gun wherein a G overlapping focusing electrode is formed toencompass a portion of the adjacent duodiameter G and G electrodes on either side thereof. Since the focusing voltage in this type of gun is normally within the range of '20O to +500 volts it is referred to as employing a low-voltage focusing lens. From the viewpoint of the manufacturer of television equipment, a cathode ray tube with low voltage focusing is desirable as such voltage is readily and economically available in a typical television receiver.

The assembly of bipotential lens guns into a multiple gun structure is conventionally accomplished by aligning the several electrode elements of each gun on an internally positioned mandrel oriented at the desired angle and extending through the gun elements. With the respective gun electrodes so relatedly positioned, heated insulating rods are simultaneously applied by a beading operation to studding support means projecting from the gun electrodes to integrate the several guns into the mount structure, whereupon, the supporting mandrel is slidably removed from within each aligned gun.

In the overlapping unipotential lens guns, the focusing G electrode has a larger diameter than the adjacent G and G electrodes on either side thereof. Thus, guns of this type cannot be assembled by utilizing withdrawable internal mandrels, as a mandrel which is small enough to go through the G and G electrodes cannot support the larger diametered focusing G electrode.

One type of unipotential lens gun known to the art employs a short focus 6., electrode which has an inside diameter equal to that of the G and G elements on either side thereof and which does not overlap or encompass these adjacent electrodes. While this short focus lens unipotential gun lends itself to internal mandrel assembly means, it is functionally inferior to the overlapping lens type. In the short focus lens gun it is necessary to use a very short G focus electrode, which may be less than 0.125 inch in length, to obtain a focus voltage in the desired region of Within a few hundred volts of cathode voltage. The short G length makes proper alignment of this element with the adjacent elements difficult to achieve and maintain. In addition, the open gaps between the focusing G and the adjacent electrodes subjects the insulating rods to electron charging effect which not only results in distortion of the electron beam being focused but also increases the likelihood of inter-electrode voltage breakdown or arcing.

It is possible to bead the electron guns individually and then assemble the several guns into an integrated mount structure, but this produces an 'unwieldly and awkward gun structure having a bulk much larger than desired for the current state of the art. In addition, past experience has shown that the integration of pre-assembled guns into a multiple gun structure introduces troublesome alignment problems due to the inherent tolerances present in each of the gun assemblies. Thus, it is extremely difiicult to consistently achieve beam landings of desired quality.

Objects and summary of the invention It is an object of the invention to reduce the aforementioned disadvantages and to economically fabricate a compact multiple electron gun mount structure that maintains desired focus over the whole screen under varying beam current conditions.

Another object is the provision of a rigid multiple electron gun structure wherein each low-voltage focusing gun is an assembly of sequentially aligned electrodes in interspaced relationship.

A further object is to provide improved means for fabricating a compact multiple electron gun structure employing Overlapping low-voltage focusing lens guns therein.

A still further object is to provide a method for assembling an improved multiple electron gun structure having desired electron optics and alignment.

The foregoing objects are achieved in one aspect of the invention by the provision of a cathode ray tube multiple electron gun structure having therein three unipotential low-voltage focusing lens guns employing overlapping focusing electrodes. The plurality of successive cylindrical electrodes of each gun are axially aligned in sequential order from an end or first electrode having an external maximum alignment diameter. Each successive electrode therefrom has an external maximum alignment diameter which is at least equal to the maximum diameter of the preceding electrode. Fabrication of the unipotential multiple gun structure is facilitated by a plurality of assembly support means having electrode support segments for each gun formed to be compatible with a portion of the external curvature effected by the alignment diameter of each electrode. This provides for each gun a cradle-like aligned arrangement of interspaced electrodes each of which has a portion of its cylindrical surface confined within its respective support segment, while another portion of its surface and its studding means are exposed in a sequential longitudinal manner. The loaded support means are relatively oriented to enable a portion of the exposed cylindrical surface of each electrode to contact a common central support post and be confined thereagainst to facilitate electrode alignment. The exposed studs are then embedded in heated insulated rods to retain the desired gun alignments. With the removal of the electrode support means and the slidable withdrawal of the common support post, there is provided a compact multiple electron gun structure that exhibits performance and fabrication advantages heretofore unattained.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the accompanying drawings.

Brief description of the drawings FIGURE 1 is a plan view of a cathode ray tube;

FIGURE 2 is an enlarged view of the multiple electron gun structure utilized in the tube shown in FIGURE 1 taken along the line 22 of FIGURE 3;

FIGURE 3 is an end view of the multiple electron gun strutcure taken along the line 33 of FIGURE 2;

FIGURE 4 is a view illustrating the assembly means for fabricating the multiple gun structure taken along the line 44 of FIGURE 5;

FIGURE 5 is an end view showing the assembling means of FIGURE 4 taken along the line 55 thereof;

FIGURES 6 and 7 are partial plan views of individual electron guns of the multiple gun structure showing the relationship between the G and G electrodes;

FIGURE 8 is an exploded perspective showing the arrangement of the electrode support means;

FIGURE 9 is an elevational view showing an embodiment of the common support post;

FIGURE 10 is a perspective view illustrating another embodiment of the support post;

FIGURE 11 is a longitudinal sectional of the embodiment shown in FIGURE 10 taken along the line 1111 thereof; and

FIGURES 12 and 13 are plan views showing cross-sectional embodiments of the common support post.

Description of the preferred embodiment With reference to the drawings, FIGURE 1 illustrates a typical plural beam shadow mask type cathode ray tube 11 having an axis 12 therein. Suitably disposed within the neck portion of the envelope 13 is a multiple gun structure 14 wherein, for example, three electron guns 15 are relatedly positioned approximately 120 degrees apart to provide three electron beams 17. Externally positioned coils 19 are generally utilized to deflect these beams over the raster area and consummate convergence at the apertured structure or shadow mask 21 to pass therethrough and impinge upon the cathodoluminescent screen 23 spaced therebeneath. To facilitate the above-mentioned convergence of the separate beams 17 over the entire screen, external dynamic convergence magnets 25 are conventionally employed in conjunction with an internal convergence assembly 27 positioned on the front or screen directed end of the multiple electron gun structure 14. In this specification, the convergence assembly is not considered as part of the multiple gun structure of the invention since it is attached to the unified gun structure subsequent to the fabrication thereof. Therefore, little reference will be made to the convergence assembly herein.

In greater detail, there is illustrated in FIGURE 2 an enlargement of the multiple gun structure 14 in which, to enhance clarity, only two of the three electron guns 15 are shown. These are unipotential, low-voltage focusing lens guns employing overlapping focusing electrodes. Structurally, each electron gun comprises an electron source or cathode 29 oriented within a G control electrode 31, a G screen electrode 33, and a G first anode portion arranged substantially in axial alignment to provide the source, control, pre-focusing and acceleration for electron beam 17 An electrostatic focusing assembly comprising a G first lens cup 37, a G focusing electrode 39, and a G accelerating electrode having a second lens cup 41 is shown mounted in substantially axial alignment with the aforementioned electrodes upon a plurality of common securement means such as insulating support rods 43. Each of the electrodes is suitably supported by studding means 45 embedded in the respective insulating rods to provide the integrated multiple gun mount structure 14.

The relationship of the three electron guns is shown in FIGURES 1 and 2 wherein the individual guns are positioned about the axis 12' of the unified mount structure. To promote clarity, the subsequently attached convergence assembly 27 is noted in phantom as an undetailed structure.

It will be noted in the embodiment shown, that the successive electrodes comprising each gun, beginning with an end or G electrode thereof, have exterior alignment diameters that are equal to or greater than the maximum diameter of the preceding electrode. The substantially cup-shaped G and G electrodes, 31, and 33 respectively, have external maximum alignment diameters 47 and 49 that are substantially equal. The G electrode has an outwardly rolled peripheral edge portion or corona ring 51 having a maximum external diameter 53 greater than the alignment diameter 49 thereof. The G composite electrode 34 has an external alignment diameter 55 which is at least equal to the G corona ring external diameter 53. The first anode portion 35 of the G electrode, having an external diameter 57 smaller than the G alignment diameter 55, is formed for spaced orientation relative to the interior of the G electrode 33. The first lens cup 37 of the multi-diameter G electrode is likewise of reduced external diameter 59. Spaced therefrom and in alignment therewith is the duo-diameter G electrode 40 having an external alignment diameter 61. The second lens cup portion 41 thereof has an external diameter 63 similar to that of the opposed first lens cup 37.

Formed to coaxially encompass the aforementioned lens cups in a spaced and substantially overlapping relationship, is the cylindrical G focusing electrode 39 having an external alignment diameter 65 which is substantially equal to the external alignment diameters 55 and 61' of the respective adjacent G and G electrodes. To reduce arcing possibilities, the peripheral edges 66 of the G focusing electrode are polished to be free of burrs or projections thereon.

It has been found that an overlapping G electrode having a circumferential dimension or alignment diameter substantially equal to that of the electrodes on either side thereof has several advantages in the multiple gun structure as described herein. First, even though several electron guns are in closely spaced relationship, enhanced shielding is provided to prevent beam distortion in each low-voltage focusing lens. Secondly, improved shielding is also provided in the reverse manner to prevent charging of the insulating support rods which greatly reduces the likelihood of voltage breakdown or arcing; and, thirdly, it has been found that the similar alignment diameters of the aforementioned electrodes in each of the several guns provides an alignment relationship between the guns which promotes the facile integration of the compact multiple gun structure.

With reference to FIGURES 4, 5, and 8, the related assembly of the several guns is shown wherein, beginning with the end or G electrode of each gun, each successive electrode therefrom has an external alignment diameter at least equal to that of the preceding electrode. To assemble each of the several guns, there is, beginning with the G electrode 31 having the cathode 29 positioned therein, a plurality of integrated external support means 93, in the form of related individual electrode support segments with electrode spacing separators providing longitudinal inter-spacing therebetween. Each electrode support segment is dimensionally formed according to the respective electrode alignment diameter to be compatible with a portion of the external curvature of the electrode to provide a cradle-like alignment arrangement. Each of the several segments has an aligned aperture 67 therein formed to accommodate an alignment rod 68 which is inserted therethrough to provide an integrated support means for the electrodes of each gun, the second segments and spacers being suitably retained in desired orientation and alignment by afiixing means 69. For example, the G control electrode 31 is loaded into the compatible support segment 71. lSuccessively therefrom, the G screen electrode is positioned in the G support segment 75 being separated from the G electrode by the G G spacer 77. The G G and G electrodes 34, 39, and 40 are seated in the formed G G and G support segments 79, =81, and 83 respectively, with the spacers 85, 87, and 89 therebetween in sequential order with each electrode having a portion of its cylindrical surface along with its studding exposed in a sequential longitudinal manner.

The several loaded support means '93 are then positioned in similar lateral relationship in a suitable seating means such as seating holder 95. Several equi-spaced holes 97 therein accommodate the lower protruding end of each alignment rod 68 to provide positioning of the aligned electrodes of each gun about a common central support post 99 oriented in the holder. The central support post is equi-distantly positioned relative to the aligned electrodes of each gun in a manner so that the exposed cylindrical surface of each electrode of each gun is adjacent thereto.

Securing means for clamping the several positioned support means 93 in an equi-distant manner relative to the common central support post 99 is facilitated by utilizing cap 101 having cavities therein to receive the ends of the individual alignment rods 68 and central support post 99. Consummation of the clamping step diametrically confines the respective suucessive electrodes of each gun in spaced longitudinal alignment between the support segments and the central support post. In this manner, the

similar electrodes of each gun are laterally oriented in spaced adjacency with one another.

With all electrodes securely clamped in their respective alignment positions heated insulating support rods 43 are simultaneously applied, by means not shown, to embed therein the plurality of exposed electrode studding means 45. Thus, the electrodes of the several guns are locked into compact aligned confinement.

Release of the clamping means by removing the cap 101 and freeing the alignment rods 68 from the seating holder allows the support segments and spacers of electrode support means to move free from the insulative rod supported electrodes. Removal of the common support post 99 is consummated in a slidable withdrawing manner from between the adjacently oriented end electrodes of the multiple electron gun mount structure.

It will be noted that in the example given, the several electron guns are tilted with reference to the mount structure axis 12'. In the tube of this instance, the axis of the mount structure is coincidental with the tube axis 12. The mount structure shown in FIGURES 2, 3, 4 and 5, the assembly of which has been described, has the individual guns angularly tilted toward the tube axis with the terminal or G electrodes being nearest thereto. To achieve this desired tilt, the common support post 99 is in the form of a tapered pin having a center line 100 coincidental with the axis 12' of the mount structure. The external electrode support means for each gun is positioned at a compatible angle in accordance with the taper of the pin thereby maintaining the proper dimensional relationship to facilitate the accommodation of te respective electrodes confined therebetween. Since the G1 and G electrodes have alignment diameters that are less than those of the successive G G and G electrodes, the common support post 99 has a stepped or dimentionally graduated taper which facilitates both electrode alignment and subsequent post withdrawal; the larger diametrically tapered dimension 103 being adjacent the G and G electrodes of smaller diameter and the smaller diametrical tapered dimension 105 being contiguous with the larger diametered G to G electrodes. With the central common support post or pin having at least one dimensional step therein, transitional to a sequential change in pin cross-sectional dimensions, the larger cross-sectional dimension thereof is adjacent the end electrode to facilitate post-fabrication withdrawal of the pin.

If desired, although not shown, the several electron guns of the integrated mount structure can be tilted away from the tube axis with the G electrodes being nearest thereto. In this instance, in keeping with the teaching of this invention, the terminal or G electrode would be considered as the end electrode with the G G G and G being successive electrodes in reverse order therefrom. Thus, the assembly of the mount structure would be inverted to enable withdrawal of the common support post therefrom upon completion of the fabrication procedure.

It is to be understood that a multiple gun structure having substantially parallel positioning of the guns therein can be fabricated by utilizing a common support post or pin similar to that shown in FIGURE 4 but which has no taper therein.

In FIGURES 6 and 7 other embodiments of the G and G electrode relationship are shown wherein the G screen electrode 33" in FIGURE -6 has an inwardly rolled corona ring 51'. This enables the G alignment diameter 49 to substantially equal the G alignment diameter 55. Similar diametrical relationships are evidenced in FIGURE 7 where the G electrode has a burrfree edge 32. Thus, the individual electron guns in the multiple structure can be fabricated wherein all of the gun electrodes are of substantially the same external alignment diameters.

Further delineation of the common support post is made with reference to FIGURE 9 wherein the common support means or post 109 has at least one longitudinal support surface 111 that is substantially parallel with the mount structure axis 12 extending substantially axially therethrough. A support post of this type is utilized to assemble the electron guns in parallel relationship. If it is desired to orient one or more guns in parallel or different angular relationships or tilts, with reference to the axis 12 of the mount structure, another embodiment of the common support rod 115 shown in FIGURES and 11 can be utilized wherein at least one portion of the longitudinal surface 117 is substantially parallel with the axis while one or more portions of the longitudinal surface 119' are angular thereto. The angular relationship of the common support surface to the mount structure axis for all embodiments of the withdrawable post can be referenced from a common intersecting plane 121 perpendicular to the axis 12', wherein the intersection of the plane with the common support surface forms in the direction of support withdrawal at least one exterior having a value not exceeding 90.

In FIGURE 12 another cross-sectional embodiment of the common support post is shown and relates to any portion or portions of the post contacted by electrodes. The substantially triangular embodiment 123 has three longitudinal sides thereon and is oriented in a manner whereby each side thereof provides a surface 124 against which an array of gun electrodes retained by said electrode support means is positioned to consummate gun alignment.

There is shown in FIGURE 13 still another crosssectional embodiment of the common support means, similarly oriented as that illustrated in FIGURE 12, wherein the pin 125 has three longitudinal flutes 126 formed therein. These flutes are equi-spaced from the pin center line 100 and from one another with lands 128 therebetween. As previously mentioned, the center lines 100 of the respective pins are coincidental with the mount structure axis 12'. Each flute is of an arcuate cross-sec tional formation 127, so shaped to compatibly accommodate a circumferential portion of the respective electrodes in each gun. The orientation of the pin is such that each flute provides an arcuate contact surface against which a surface portion of each electrode in each gun array, retained by said electrode support means, is positioned to consummate gun alignment.

There is thus provided a compact multiple electron gun mount structure of the low-voltage, overlapping focusing lens variety that is economical to fabricate and wherein each successive electrode has a sequential alignment diameter that is at least equal to the maximum diameter of the preceding electrode. Means for facile assembly are provided wherein the aligned electrodes of the several guns are positioned with external portions adjacent a common support post which is withdrawable from the completed mount structure. The resultant multiple gun structure along with the means and method of assembly thereof are achievements heretofore unattained.

While there has been shown an described what is at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

I claim:

1. Means for assembling an improved multiple electron gun cathode ray tube mount structure having an axis about which at least two overlapping, unipotential, lowvoltage focusing lens electron guns are relatedly mounted by studding means on insulating rods, each gun having a plurality of successive cylindrical electrodes, one being an overlapping focusing electrode formed to encompass a portion of adjacent multi-diameter electrodes on either side thereof, the end electrode in each gun having an external maximum alignment diameter with each successive electrode therefrom having an external alignment diameter at least equal to the maximum diameter of the preceding electrode, said assembling means comprising:

a plurality of integrated external electrode support means, one for each gun, comprising several longitudinally related individual electrode support segments, each of said segments having an electrode support portion formed in accordance with said successive alignment diameters to be compatible with a portion of the external curvature of each respective cylindrical electrode beginning with said end electrode to provide a related cradle-like aligned arrangement for said gun electrodes to thereby facilitate alignment thereof, said support means being formed to be removable from said electrodes subsequent to mount fabrication;

spacing means separating said electrode support segments to provide longitudinal inter-spacing between said electrodes, said spacing means being formed to be removable from between said electrodes subsequent to mount fabrication;

a common longitudinally oriented support means having a center line coincidental with said tube mount structure axis, said support means being equi-distantly positioned relative to said plurality of electrode-orienting external support means for said guns, said common support means being formed for withdrawal from between said guns subsequent to mount fabrication, said common support means having said tube mount structure axis substantially extending therethrough, said tube mount structure axis and the surface of said common support being intersected by a common plane perpendicular to said tube mount structure axis, said plane and said common support surface forming, in the direction of said support withdrawal, at least one exterior angle having a value not exceeding seating means for positioning said plurality of external support means with said electrodes accommodated therein in spaced relationship to said common support means, said spaced relationship being substantially equal to said external alignment diameters of the respective electrodes in each gun;

securing means for holding said plurality of external support means relative to said common support means to diametrically confine therebetween said electrode in spaced longitudinal alignment, said electrode having studding means projecting therefrom in an exposed longitudinal manner; and

beading means to facilitate embeddment of said electrode studding means in said insulating rods to thereby provide a compact multiple electron gun mount structure that retains unity when freed of said assembling means.

2. A cathode ray tube multiple electron gun assembling means according to claim 1 wherein said common support means is a tapered pin formed to provide angular tilting of said individual electron guns relative to said tube axis, said external support means for each gun being positionally oriented at a compatible angle in accordance with said taper.

3. A cathode ray tube multiple electron gun assembling means according to claim 1 wherein said common support means is in the form of a pin having at least one dimensional step therein transitional to a sequential change in pin cross-sectional dimensions, the larger cross-sectional dimension being adjacent to said end electrode.

4. A cathode ray tube multiple electron gun assembling means according to claim 1 wherein three electron guns are arranged in a substantially triad relationship, said common support means being a formed pin of substantially triangular cross-section having three longitudinal sides thereon, said pin being oriented in a manner whereby each of said sides provides a surface against which a surface portion of each electrode in each gun array retained by said electrode support means is positioned to consummate gun alignment.

5. A cathode ray tube multiple electron gun assembling i means according to claim 1 wherein three electron guns are arranged in a substantially triad relationship, said common support means being a pin having three longitudinal flutes formed therein, said flutes being equi-spaced from said center line and from one another with lands therebetween, each flute having an arcuate cross-section formed to accommodate a circumferential portion of the respective electrodes in each gun, said pin being oriented in a manner whereby each of said flutes provides contact surface against which a surface portion of each electrode in each gun array retained by said electrode support means is positioned to consummate gun alignment.

References Cited UNITED STATES PATENTS CHARLIE T. MOON, Primary Examiner R. B. LAZARUS, Assistant Examiner 

